The present invention relates to an automobile control system and method having an information processing unit which shares control data with other information processing units provided in the same or different control systems.
An automobile control system for controlling a control target such as an engine or transmission mounted on an automobile is provided with a microcomputer (MC) as an information processing unit for performing arithmetic operations for controlling the control target. The control system is generally constructed as shown in FIG. 21. A microcomputer 600 in an engine ECU (electronic control unit) takes in various signals such as engine rotation pulse, automobile speed pulse, and shift-lever position signal through an input/output circuit 602. It performs arithmetic process for controlling an engine (not shown) through actuators.
Various control data that represent physical values such as the engine speed calculated by the microcomputer 600 in the engine ECU are sent out from the microcomputer 600 to a communication IC 604 at the predetermined timing, and sent out further to a driver circuit 606 through an internal communication line. Other ECUs (communication opponents) such as a meter ECU receive supplied control data through an external communication line, and use these data for controlling respective control targets.
In the automobile control system that involves communication among ECUs, in some cases, the resolution of data required in each ECU is different even though the same type of control data is processed. For example, the engine ECU calculates the control quantity for controlling the engine by processing the engine speed control data with the resolution of 50/256 (approximately 0.195) rpm per LSB (per least significant 1 bit). On the other hand, the meter ECU processes the engine speed control data with the resolution of 1 rpm per LSB. Thus, the control data to be transmitted from one ECU to another ECU should be converted before the transmission so that the resolution or accuracy of the data should match each other.
As exemplified in FIG. 22, in the conventional ECU, a plurality of accuracy-conversion programs (LSB conversion programs 1 and 2) to be executed by the microcomputer of the side that transmits the control data are provided for each preset conversion period. Each LSB conversion program performs accuracy conversion process (LSB conversion process) corresponding to the resolution involved in the communication opponent side on each of the plurality of control data. The LSB conversion program 1 for DATA 1-DATA 10 is activated every 16 ms and LSB conversion program 2 for DATA 11-DATA 30 is activated every 64 ms. Specifically, the conventional ECU LSB-converts each control data to be transmitted periodically, and retrieves a control data to be transmitted selectively from among LSB-converted control data at the transmission timing, for example, that occurs every predetermined transmission period. It transmits it to the communication opponent. Therefore, the execution period of each LSB conversion programs 1 and 2 is set to a time shorter than the transmission period transmitted to the communication opponent.
When the content of the LSB conversion is to be changed or when the transmission period of the control data is to be changed, many steps of the program must be revised when the content of the LSB conversion or transmission period is changed. This revision or correction is not simple. Furthermore it is disadvantageous in that it is impossible to specify particular steps of the program to be revised without understanding of the whole program.
Further, the microcomputer 604 does not transmit various data individually but transmits these data in a packet after arranging a plurality of types of data such as the engine speed data, automobile speed data, and fail-safe data for activating a warning lamp. In this instance, generally, header information corresponding to a communication protocol is added to the head of packet data as shown in FIG. 23.
The packet data is categorized into two types. One is the data to be transmitted periodically with a predetermined time interval, and the other is the data to be transmitted immediately after update of the content. Further, the transmission timing is categorized into two types. One is a regular transmission which is effected at regular time interval, and the other is an event transmission which is effected only when a predetermined event such as a completion of 20 times of fuel injection occurs.
In the conventional system, all the packet data to be transmitted are generated every predetermined time interval, even though different types of packet data are transmitted at every each transmission timing. Thus, all the packet data must be updated and stored successively always, requiring a large memory area and a lot of ineffective process. When the type of the data that constitutes each packet data or the location position of the data in a packet data is to be changed, it is required to check the packet generation program in detail for revision, also requiring a lot of time and labor. When the transmission period of any packet data is to be changed shorter, the process must be corrected so that the packet data is generated by means of a program executed at shorter period than the transmission period after change, requiring understanding of the whole program.
It is therefore an object of the present invention to provide an automobile control system that requires a minimum number of program revisions, even when a predetermined process such as an accuracy conversion or packet data generation required for transmitting control data to a communication opponent is changed.
According to a first aspect of the present invention, a transmission command is issued to indicate control data to be transmitted this time to a communication opponent at the predetermined transmission timing, and the control data indicated by the transmission command is retrieved from a memory unit. In this instance, a conversion program corresponding to the control data indicated by the transmission command is specified. The specified conversion program is activated to process the retrieved control data to thereby subject the control data indicated by the transmission command to an accuracy conversion process. Furthermore, the accuracy-converted control data is transmitted to the communication opponent after the accuracy conversion process.
According to a second aspect of the present invention, a first data table and a second data table are provided. The first data table lists the type number of the transmission target data that constitutes a packet data of the packet number for each packet number that is the identification number of the packet data. The second data table lists the packet number of the packet data that includes the transmission target data of the type number as component and the location position information for indicating the location position in the packet data of the transmission target data of the type number for each type number of the transmission target data. The data map for defining the information used for generating a regular transmission packet data and an event transmission packet data is divided into the first data table and the second data table. As a result, in any of the regular transmission and the event transmission, a packet data to be transmitted at that time can be generated quickly. It is not necessary to generate periodically the packet data to be transmitted beforehand, and thus the redundant process and memory area are eliminated. That is, the transmission target packet data can be generated quickly and efficiently when data transmission is required not only in the regular transmission but also in the event transmission.